Drive unit incorporating backlash eliminator means



M ww- Sept. 23, 1958 DRIVE UNIT INCORPORATING BACKLASH ELIMINATOR MEANS Filed Nov. 12, 1954 C. M. FRITZ ET AL 3 Sheets-Sheet 1 a Ive/Viv Sept. 23, 1958 c. M. FRITZ ET AL 2,852,945

DRIVE UNIT INCORPORATING BACKLASH ELIMINATOR MEANS Filed NOV. 12, 1954 SSheets-Sheet 2 Sept. 23, 1958 c. M. FRITZ ET AL 2,852,945

DRIVE UNIT INCORFORATING BACKLASH ELIMINATOR MEANS 5 Sheets-Sheet 5 Filed Nov. 12, 1954 55 I an: 5/

alinillll llllltm GOA/E50 M, FE/TZ JOA K/ F, 59/652 INVEN'IORE) States Patent @fifice 2,852,945 Patented Sept. 23, 1958 DRIVE UNE'F. INQ QREGRATHNG BACKLASH ELIMINATOR MEANS Conrad ME. Fritz, West Los Angeles, and John A. Baker, North Hollywood, Qahifi, assignors, by inesne assign ments, to Philip :3. Allen, (Carlsbad, Calif., an individual Application November 12, 1%4, Serial No. 468,180

1.5 Claims. (Cl. 74--24) This invention relates to a drive unit, and more particularly to a means for eliminating backlash or play between a shaft and elements which effect both rotation thereof and longitudinal movement thereof with a predetermined cam motion.

There are many mechanisms in which it is necessary that a shaft be rotated or indexed about its axis, and also shifted longitudinally thereof, with a precision movement making any backlash or play extremely undesirable or intolerable. One such mechanism is set forth in co-pending application Serial No. 468,178 filed November 12, 1954, for Automatic Photographic Apparatus. The cited application describes and claims an automatic photographic apparatus which is an improvement over the structures shown in Patents 2,3 80,378 and 2,541,016, issued to Philip S. Allen respectively on July 31, 1945, and February 13, 1951.

in the application referred to, a structure is shown in which a plurality of tanks containing developer and rinse solutions are disposed generally in a circle, and a vertical support shaft is provided at the center of the circle for the purpose of supporting at its upper end a film carrier means, the latter being adapted to hold exposed film to be developed by dipping into the various tanks. In order to cause the film carrier and contained film to be clipped sequentially into the tanks so that the film may be operated upon the various developer and rinse fluids, it is necessary that the support shaft be not only longitudinally reciprocated but also rotated or indexed about its axis. More specifically, the support shaft is first shifted longitudinally to an extreme elevated position at which the film carrier is registered and closely adjacent a conveyor means adapted to deliver an exposed film strip thereto from a camera unit, is then lowered slightly to clear the carrier of the conveyor means and thus prevent fouling therebetween, is then indexed to move the carrier from above one developer tank to above an adjacent one, and is then lowered and reciprocated to effect dipping of the carrier and contained film into a developer solution and also to agitate such solution for more effective developing action.

In the above described photographic apparatus, forming the subject matter of the co-pending application Serial No. 468,178, it is necessary that the film carrier be registered accurately with the film conveyor means when the shaft is in the indicated extreme upper position, otherwise there will be fouling of the elements and also faulty delivery of the exposed film from the camera to the film carrier. To effect such accurate registry it is necessary that there be no backlash or play between the shaft and the drive means which effects indexing and reciprocation thereof. Such absence of backlash must also result when the carrier is in the indicated slightly lower position during indexing thereof, this being in order to insure proper operation of certain carrier selector and carrier cam means. At all other times backlash or play is permissible and, in fact, desirable in order to minimize friction during the longitudinal shifting of the support shaft as the carrier is dipped into and out of the tank.

It is to be understood that the automatic photographic apparatus described in application Serial No. 468,178 is only typical of a number of mechanisms or machines requiring drives of the type indicated, and in which backlash is undesirable at certain portions of the drive cycle but is desirable or permissible at other portions of the cycle. Such machines would include certain machine tools, control apparatus, etc.

In view of the above factors characteristic of drives of the type indicated, it is an object of the present invention to provide an improved drive for effecting both longitudinal displacement and rotation of a shaft and thus of the elements connected thereto, said drive incorporating means to prevent backlash or play between the shaft and its driving components when the shaft is at predetermined longitudinal positions.

A further object is to provide means for shifting a shaft longitudinally in accordance with a predetermined cam motion, and for intermittently rotating or indexing the shaft in such a way that it will be in precise predetermined stations during certain portions of the cam cycle.

An additional object is to provide a novel cam drive for effecting longitudinal shifting of a driven element and for insuring that said driven element will be at predetermined stations during critical portions of the cam cycle.

These and other objects and advantages of the invention will be more fully set forth in the following specification and claims considered in connection with the attached drawings to which they relate.

In the drawings:

Figure 1 is a vertical sectional view taken along line 11 of Figure 2 and showing the drive unit of the invention, the parts being illustrated in their positions at which the driven shaft is at its lowermost elevation;

Figure 2 is a horizontal sectional view taken along the broken line 2-2 of Figure 1;

Figure 3 is a vertical sectional view taken on line 33 of Figure 2 and illustrating the parts in the same positions as are shown in Figure 1;

Figure 4 is a vertical sectional view corresponding generally to Figure 1 but illustrating the parts in their positions causing the vertical support shaft to be in its uppermost position, parts being broken away to illustrate the operation of the antibacklash means when the shaft is in said uppermost position;

Figure 5 is a fragmentary sectional view taken along line 5-5 of Figure 1 and illustrating the means for providing a positive cam action at a critical portion of the cam cycle;

Figure 6 is a fragmentary horizontal sectional view on line 6-6 of Figure 4;

Figure 7 is a fragmentary perspective View illustrating the intermittent drive disc and actuator as positioned to rotate the associated gear and thus the vertical support shaft;

Figure 8 is a fragmentary edge View of the intermittent drive disc and actuator, as viewed generally from the left side of Figure 7; and

Figure 9 is an enlarged horizontal fragmentary section taken along line 99 of Figure 4. p

The invention will be described as employed in effecting both vertical cam movement and rotation or indexing of a film strip carrier means, indicated fragmentarily at 23 in Figure 3, for the purpose of effecting sequential clipping of exposed film strips carried by film carrier means 23 into a number of developer and rinse tanks, not shown, arranged in a circle therearound. To effect the vertical reciprocation and also rotation of the film strip carrier means 23, the drive 24 of the invention is mounted on a suitable support means, not shown, and is powered by an electric motor indicated schematically at 26 in Figure 1. Thedrive 24 is also shown and described, with less detail, in the previously .cited co-pending application Serial .No. 468,178.

The drive 24 includes a suitable cast metal housing 27 having upper and lower bearing sleeves 28 and 29 suitably secured ,thereto'in axial alignment with each-other. Asfshown best in Figure 3, the lower bearing sleeve 29 extends for. a substantial distance beneath housing 27 and also for a substantial distance interiorly thereof. The upperbearing sleeve 28 preferably terminates adjacent thezupper portions of the unshown developer tanks. A

racksleeve 31 is mounted within the lower bearing sleeve 2'9Jby means .to be described hereinafter, and within upper bearing-sleeve 28 by means of bushings 32 per- Initting free sliding verticalhmovement. The rack sleeve 31 extends upwardly to the film strip carrier means 23, aslillustrated in Figure 3, and engages the bottom of the'latterin such a way thatrelative rotational movement is permitted. Mounted axially of rack sleeve 31 is a rotation rod 33 having a reduced upper end portion 34 (Figure 3) which ,is non-rotatably secured by means of a nut 36 and pin 37-to the film strip carrier means 23. The rotation rod 33 extends for the full length of the rack sleeve and rotates in bushings 38 in the latter.

The lower. bearing, sleeve 29 is provided with a pair of'bushings 39 to rotatably receive a key sleeve 41 best shown in Figure 3. Agear 42 is mounted horizontally aroundv the upper and exposed part of key sleeve 41, generally at the center of housing 27, and is provided with a sleeve portion 43 which seats rotatably on the upper end of a bushing 39 and islocked to the, key sleeve by means of a set-screw 44. Mounted longitudinally within key sleeve 41 by means of screws 46 is a key 47 of rectangular section (Figure 9) and which extends for substantially the full length of the key sleeve as illustrated in'Figure 3.

'Atthe upper end .ofkeysleevc 41, and diametrically opposite: key 47, ,as shown in Figure 9, is mounted a b31148. The ball 48 is disposed within a precision bushing 49 extending through an aperture in the key sleeve, the bushing being so relateed to the, ball that the latter may move radially of the key sleeve, within limits determined by ears 50, but is maintained againstmovement circumferentially or longitudinally thereof. A leaf spring 51 is mounted exteriorly of the key sleeve and adapted to press ball 48 radially inwardly.

' 'The lower end of rotation rod 33 is reduced in diameter and inserted into a plug 52, there being a pin 53 provided to hold the plug in position and prevent rotation thereof relative to the rod 33. One side of plug 52 is formed with a keyway 54 of rectangular section and which is adapted to fit loosely over the rectangular key 47 indicated above. Diametrically oppositethe keyway 54 is a second keyway. 56, this keyway being of V-section instead of rectangular section. The plug 52 seats against the lower end of rack sleeve 31 and in such a way that the plug may rotate relative thereto.

The gear 42 is provided with fourteen teeth 57 as illustrated in Figure 6. It follows that each time the gear 42 is shifted of a revolution, due to the shifting of one tooth 57 into the position previously occupied by the adjacent tooth and as will be described subsequently, the film strip carrier, means 23 will also .be rotated or indexed 1 of a revolution, an amount selected so that each, of itsv film carrier components is shifted from above one developer tank to above .the adjacent tank. The connection between;.gear,.42 and the film strip carrier means 23 is effected firstby the set screw 44, which rotates thekeyvsleeve 41 withthergear, and then by the key 47 and ball 48-which serve to rotate the plug 52 withthev key sleeve. \Since plug 52 .is; pinned; by the pin 15340: rotation $011.53, thceotationnftheplug .cffects.

rotation of rod 33 and thus of the film strip carrier means 23, the latter being non-rotatably secured to the upper end of the rotation rod as previously described.

The described rotational movements take place without effecting rotation of rack sleeve 31, this element being held against rotation due to meshing of its teeth with the associated pinion. However, vertical movement of the rack sleeve 31 operates either to lift the film strip carrier means 23 or effect lowering thereof since the ends of the rack sleeve bear respectively against film strip carrier means 23 and plug 52.

It is a feature of the invention that upward and down ward movement of the rack sleeve 31 and plug 52 is for the most part relatively frictionless since, as stated heretofore, the keyway 54 is only a loose fit over key 47. This loose fit means that the film strip carriers are not perfectly centered in their various indexed positions as they move vertically during the major portion of a stroke. However, as soon as the plug 52 arrives at an upper point (Figure 4) adjacent ball 48, when the rack sleeve 31"is near the upper end of its stroke, ball 48 rides into the V-shaped keyway 56 (Figures 4 and 9) to effect perfect centering of the plug 52 and thus of rotation rod 33 and the film strip carrier means. Any backlash or play between the film strip carrier means and key sleeve 41 is accordingly eliminated when the carrier means is in the elevated position at which it is indexed, and at which it makes contact with various film conveyor mechanisms associated therewith. However, this absence of play doesnot result in excessive friction during the major portion of the vertical movement of the described elements sinceit is only the loose key 47 that thenmaintains approximate alignment. As a further important means for reducing friction while providing perfect centering, a sphere 33a is provided at the upper end of rod 33 for insertion into a precision socket 331; (Figure 3) on a shelf or stationary support 330 when carrier means 23 is inits two upper positions. This construction permits the bearings for rack sleeve 31 (especially upper bushing 32) to be relatively loose and frictionless without impairing the centering of the carrier.

Proceeding next to a description of the means which cooperate with rack sleeve 31 to effect its vertical movement, and with gear v42 to effect its intermittent ,rotational movement, the shaft of motor 26 is provided with a pulley 58 connected through a belt 59 to a pulley 61 on a shaft 62 which is journalled in the 5 walls of housing 27 by means of ball-bearings 63 best t the ball-bearings 68 illustrated in Figure 2. Shaft 67,,is

thus rotated by the motor and serves the function of driving an intermittent drive disc 69, the latter being fixedly secured to the end of shaft 67 remote from gear 66 as illustrated. Disc 69 is formed with a precision bevel edge 71 which fits between two adjacent teeth 57 of :gear' 42 and effectively prevents any rotation of the gear 42 during the major portion of a drive disc revolution.

-As shown in Figures 2 and 6, disc 69 is not disposed in the. .same plane as the 'axis of gear 42, being instead disposed a substantial distance to one side of said plane. Furthermore, disc 69 has a relatively large radius as compared to the distance between shaft 67 and the adjacent gear teeth 57. It follows that longitudinal adjustmentof shaft'67 will operate to vary the closeness of engagement between bevel edge 71 and gear teeth 57. Such adjustment of shaft 67 is effected by means of nuts 701on the ends thereof.

cA rectangular notch or window 72 is formed atone pointin'the periphery of disc 69, and an actuator 73 is and..is.. provided witha slantedzcam wall.76 which is so shapedthatitwill push. one tooth 57 of gear. 42 through. the window 72 as the disc. rotates. As soon as this tooth,

57 has beenpushed through. the. window, the unnotched periphery or bevel edge 71 of.disc 69 will again operate to lock gear.42 against rotation.

In the describedmanner, therefore, gear 42 is. locked against any rotational movement except when the window 72 andactuator 73 rotate therepast, atwhich time the gearisindexed ,4 of a revolution as is the film strip carrier. means. 23. The described intermittent drive and locking .arrangemcnt cooperate with the previously described ball.48. and V-groove 56 to prevent any backlash or. play between the drive and the film strip carrier means.

Referring to. Figures 2' and .5, one wall'of gear 66 is recessed or dished to receive a cam 81, the latter being securedto the: gear as by screws 82. Cam 81 engages a-cam follower roller. 83 mounted on a gear sector 84 which has its apex mountedfor free rotational movement about a fixed shaft 86 extending parallel to shaft 67 relatively adjacent the exposed part of rack sleeve 31'. The arcuate edge. of. sector 84, remote from shaft 86, meshes with a relatively smallgear 87 which is keyed on a sleeve 88 adapted to rotate. freely relative to its' supporting. shaft 67. Also keyed on sleeve 88 is a relatively large gear 89 meshing with a pinion 91 which'is journalled on the fixed shaft 86 for free. rotation relative-thereto. The teeth of pinion 91 mesh with rack teeth. 92 -on the lower portion of rack sleeve 31, so that rotation of the. pinion will effect vertical reciprocation of the rack sleeve and thus of the film carrier means.

From the above it will be seen that rotation of worm 64 by motor 26 effects rotation of gear 66 and thus of cam 81 secured thereto. Cam follower roller 83' is thus. shifted in accordance withlthe shape of the cam to effect pivotingof. sector 84. about shaft 86. The smaller gear 87 meshed with sector. 84 is thus. driven to rotate sleeve 88 about the shaft 67'on which. it is supported, so that large gear 89 is also rotated to drive pinion 91 and thus effect. vertical movement of .racksleeve 31' and the .film strip carrier means 23 associated therewith. The direction of motor rotation is, in the illustrated example, such that shaft. 67, and thus. cam 81 and intermittent drive disc 69, rotate counterclockwise as viewedin Figures 1, 3 and 4.. Furthermore,,the elements are so related that when cam follower roller 83 engages a low pointon cam. 81 the rack. sleeve 31, and thus film carrier means 23, will be in alow position such as is shown in Figures 1 and-3. When, however, theroller is at a high point on cam 81,.the rack sleeve and film carrier will be in an upper position such as is shownin Figure 4.

Referringito Figures. 1 and 4, cam 81 is shaped with a series of rises and. depressions. 93 relatively adjacent. shaft. 67, and which. elfect upward and downward movement of the film. carriers when immersed in the tanks so-th'at agitation. of the .various developing fluids. will take place. The highest section of the cam is indicated at. 94 and. is the one elfecting positioning of film strip carrier means 23. in its uppermost position closely adjacent the indi'catedfilm strip conveyor means A second high section of. cam 81, but slightly lower than section 94, is indicated at 96 and is separated'from section 94 bya drop portion 97; The section 96 is the one effecting positioning of the film carriermeansat an elevation slightly below its uppermost position, the drop at portion 97 being sufficient to permit the film carrier means to clear the film conveyor mechanisms during indexing. The

rotated position of cam 81 relative to actuator 73 and window 72. is such that rotation or indexing of gear 42, andthus of. the filmstrip carrier, takes place only when roller 83.is on the cam section or arc 96 and the film to the diameter of roller 83.

42and film strip carrier means 23 will index and the.

latter will'engage and foul with the film conveyor means and cause damage to or breaking of the apparatus. Ac-

cordingly, and as shown in Figures 1 and 5, a pin 98 is mounted at the periphery of gear 66 opposite cam section 96 adjacent drop portion 97, and is spaced radially 'away from section 96 by a distance approximately equal It follows that a local positive cam action is provided between the pin 98 and roller 83 to insure that the latter immediately engages cam section 96 as it rides otfdrop portion97, so that dropping of the rack sleeve 31 and film strip carrier means is positive and immediate as is desired and necessary.

The operation of the drive means 24 of the invention is as follows. Let it be assumed that the parts are initially in the positions illustrated in Figure 4, with cam follower roller 83 engaging the high section 94 of cam 81 adjacent drop 97 thereof. Since the roller 83 is in engagement with high section 94, the rack sleeve 31 and thus film strip carrier means 23 are in their uppermost positions,

at which one or more of the unshown film strip carriers 'forming part of the means 23 may be adjacent and registered with a film conveyor mechanism or unit. As

illustrated in Figures 4 and 9, when the parts are in this uppermost position the V groove 56 in plug 52 at the bottom of rotation rod 33 is registered over the spring pressed ball 48. It follows that the pressing of ball 48 by spring 51 into the V-groove will effect a slight rotation of plug 52, and thus of rod 33 and the film strip carrier means 23; to bring these elements into the desired rotated position relative to the key sleeve 41. Key sleeve 41 is, in turn, held in the .correct position by means of gear 42, the teeth of which are accurately locked by the peripheral edge 71 of intermittent drive disc 69 as best illustrated in Figure 6. In addition to the described means for eliminating backlash or play, ball'33a is disposed in socket 33b to insure that carrier means 23 is accurately centered.

Energization of motor 26v will then operate through pulleys 58 and 61 and belt 59 to drive the shaft 62 and thus the worm 64 thereon. Worm 64 in turn drives gear 66, and thus cam.81 and shaft 67, in a counterclockwise direction. Rotation of cam 81 causes cam follower roller 83 to ride' down the drop 97, which action is made positive due to operation of pin 98 as previously described.

Sector 84 isthus rotated counterclockwise a slight amount, causing clockwise rotation of small gear 87, sleeve 88 and large gear 89. counterclockwise rotation of pinion 91 is thus effected, resulting in lowering of rack sleeve 31 and thus of thefilm strip carrier means 23. The drop 97 is not, however, suflicient so that plug 52 rides out of. engagement with spring pressed ball 48, which means that accurate alignment of the film strip carrier 23 will still be maintained and as described above.

The indicated rotation of shaft 67 will cause corresponding rotation of intermittent drive disc 69 from its position shown in Figure 4, at which actuator 73 is closely adjacent gear 42, to a position at which the actuator engages androtates the gear 42 one step. This operation, as described above and shown in Figures 6-8, is such that the slanted wall 76 of actuator 73 engages a tooth 57 of gear 42 and pushes the tooth through the window 72in disc 69, after which the edge 71 of disc 69 again locks the teeth of gear 42 as shown in Figure 6. Gear 42 is thusrotated one step or of a revolution, which op-.

crates through set screw 44 to rotate key sleeve 41. Rotation. of thekeysleeve in turn operates through ball 48 and key 47to rotate the plug 52 and thus rotation rod33' and the film. strip carrier means.

It is emphasized that the absence of backlash or playv during the rotation or indexing of'the film strip. carrier means; caused bythecontinued presence of ball 48 in V-groove 6, is extremely important since portions of the film strip carrier means 23 must engage certain carrier selector means, described in co-pending application Serial No. 468,178, to provide critical and important cam actions. Such cam actions might be improperly performed if the play were excessive instead of being eliminated by means of the present invention.

Continued counterclockwise rotation of shaft 67 and cam 31 causes cam follower roller 83 to ride off the cam section 95 and drop to adjacent the rises and de pressions 93. The pinion 91 is accordingly rotated counterclockwise a substantial distance to effect a very substantial lowering of the rack sleeve 31 and associated components to the position illustrated in Figures 1 and 3. The film holder portions of carrier means 23 are thus dipped into the various developer tanks and, due to the rises and depressions 93, reciprocated slightly to effect an agitation or washing action which enhances the developing operation.

It is extremely important to note that during the major portion of the described lowering of the rack sleeve 31 and associated components, the spring pressed ball 43 is out of engagement with plug 52 so that friction between these elements is eliminated. Instead, the only thing which maintains the plug 52 and film strip carrier means in approximate alignment is the rectangular key 47 in the groove 54. in this Way, therefore, the approximate alignment necessary to cause the carriers to dip into the tanks therebeneath is maintained, yet a very substantial amount of friction is eliminated due to the disengagement of the plug 52 from ball 48.

After sufficient washing and agitation have taken place, cominued operation of motor 26 causes cam follower roller 33 to ride from the Figure 1 position up to the .igh section 94 of cam 81. The resulting elevation of rack sleeve 31 is initially relatively frictionless but, after plug 52 engages ball 48, a substantial amount of friction is introduced and, in addition, the V-notch or groove 56 centers over the ball 48 to bring the film strip carrier means into the necessary accurate alignment as before. Furthermore, ball 33a rides into socket 33b to correct any miscentering that may be present due to looseness in the upper bearing 32 for rack sleeve 31.

While the particular apparatus herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as defined in the appended claims.

We claim:

l. A drive unit comprising a shaft adapted to be rigidly connected with a driven element, an intermittent drive disc means to effect intermittent rotation of said shaft about its longitudinal axis to a plurality of indexed positions, a cam unit to effect reciprocating movement of said shaft longitudinally of said axis and to a plurality of longitudinal positions, and means to prevent backlash between said shaft and said drive disc means when said shaft is in at least one of said longitudinal positions.

2. The invention as claimed in claim 1, wherein said cam unit is constructed to effect a positive cam action at at least one point in the cam cycle.

3. In a drive unit, a first member, a second member mounted longitudinally of said first member and adjacent thereto, means to move said second member longitudinally of said first member and between a plurality of predetermined positions, first key means to maintain said second member in approximate rotational alignment relative to said first member and during substantially the entire longitudinal movement thereof, and second key means to cause said second member to be in precise rotational alignment relative to said first member and dur ing only a portion of said longitudinal movement.

r 8 .4. The invention as claimed in claim 3, in which said first and second members are annular in section and are mounted concentrically relative to each other, and in which said second key means includes a spring pressed ball and cooperating V-groove.

5. In a drive unit, a bearing sleeve, a key sleeve journalled within said bearing sleeve for rotation relative thereto, a rod mounted within said key sleeve and having an enlarged plug fixedly provided at one end portion thereof, reciprocation means to shift said rod and plug longitudinally of said key sleeve, a first key mounted on said key sleeve and adapted to fit loosely into a groove in said plug, said first key extending for substantially the full length of said key sleeve, and a second key mounted at one end of said key sleeve and adapted to fit tightly into a second groove in said plug when said rod and plug are at predetermined longitudinal positions.

6. The invention as claimed in claim 5, in which said second groove is of general V-section; and said second key is a spring pressed ball mounted in said key sleeve for radial movement relative thereto.

7. The invention as claimed in claim 5, in which a gear is rigidly mounted on said key sleeve, and means are provided to effect step-by-step movement of said gear and consequent intermittent rotation of said key sleeve, plug and rod.

8. The invention as claimed in claim 5, in which said reciprocation means includes a rack sleeve interposed between said rod and key sleeve and fixed against longitudinal movement relative to said rod and plug.

9. A drive unit, comprising a bearing sleeve, a key sleeve journalled within said bearing sleeve for rotation relative thereto, a. rack sleeve mounted within said key sleeve for longitudinal movement relative thereto, a rotation rod mounted within said rack sleeve for longitudinal movement therewith and for rotation relative theret0,said rod being adapted to be connected at one end to an element to be actuated, a plug fixedly mounted on said rod at the other end thereof, a first key mounted on said key sleeve and adapted to fit loosely into a groove in said plug, said first key extending for substantially the full length of said key sleeve, a second key mounted on said key sleeve and adapted to fit tightly into a second groove in said plug when said rod and plug are at predetermined longitudinal positions, cam and pinion means to effect longitudinal movement of said rack sleeve, and intermittent drive means to effect step-by-step rotation of said key sleeve.

10. The invention as claimed in claim 9, in which said cam and pinion means include a pinion meshed with said rack sleeve, a cam follower adapted to effect rotation of said pinion, and a cam adapted to effect a predetermined movement of said cam follower.

11. The invention as claimed in claim 10, in which 'means are provided to insure engagement between said cam follower and cam during at least one portion of the cam cycle.

12. The invention as claimed in claim 9, in which said intermittent drive means comprises a gear rigidly mounted on said'key sleeve, a disc having its peripheral edge inserted between two adjacent teeth of said gear to lock said gear against rotation, said disc having a. notch in said peripheral edge and releasing said teeth when said notch is adjacent thereto, and actuator means mounted on said disc at said notch to shift one tooth of said gear through. said notch once during each revolution of said disc.

13. In a drive unit, a shaftQrneans including a notched driven disk adapted to be coupled to a motor rotating only in one direction for rotating said shaft intermittently and for reciprocating said shaft longitudinally, and socket means for centering said shaft against rotation when the same is in predetermined longitudinal positions.

14. In a drive unit, a frame having a shaft supported for rotary and axial movement, uni-directional drive means for rotating said shaft intermittently and for reciprocating said shaft axially, said means including notched means having a lost motion connection with said shaft and operable to rotate the shaft independently of the latters axial movement, means for accurately positioning said shaft and for holding the same against rotation when the shaft is in predetermined longitudinal positions while leaving the shaft free to rotate when the shaft is in other longitudinal positions.

15. In a drive unit, a shaft, means for rotating said shaft intermittently and for reciprocating said shaft longitudinally including a uni-directional power input means, and detent and socket means for accurately positioning 10 said shaft and for holding the same against rotation when the shaft is in predetermined longitudinal positions while leaving the shaft free to rotate when it is in other longitudinal positions.

References Cited in the file of this patent UNITED STATES PATENTS 286,225 Richards Oct. 9, 1883 10 2,579,092 Rockwell Dec. 18, 1951 2,596,581 Mercier May 13, 1952 2,640,362 Taylor June 2, 1953 

